1. Field of the Invention
The present invention relates to an image reading apparatus configured to read an image and to an image forming apparatus including such image reading apparatus.
2. Description of the Related Art
Various image forming apparatuses such as a copier and a facsimile are provided with an image reading apparatus configured to read an image in general. Some image reading apparatuses also include an automatic document feeder (abbreviated as “ADF” hereinafter) configured to feed a sheet such as a document sheet stacked on a stacking portion to an image reading portion. Such image reading apparatus including the ADF adopts a method of reading the image while feeding the sheet stacked on the stacking portion by the ADF to the image reading portion at a constant speed (referred to as “skimming-through” hereinafter).
By the way, there is a case of skimming through different sizes of sheets mixedly stacked on the stacking portion. However, because the different sizes of sheets have different sizes also in terms of a width of the sheet in a direction orthogonal to a sheet feeding direction (referred to simply as a “sheet width” or “widthwise” hereinafter), a position of a center (midpoint) of the sheet width is different per different size of sheet. Therefore, there is a case when the sheets are fed while being skewed, as rollers that feed and separate the sheets come in contact with parts of the sheets other than the center thereof in skimming through the mixedly stacked different sizes of sheets. When the sheets are fed askew to the image reading portion, there is a possibility that an image is read aslant by the image reading portion.
Then, Japanese Patent Application Laid-open No. 2000-118744 discloses an image reading apparatus configured to skim through different sizes of sheets mixedly stacked on a stacking portion such that a feed roller for feeding a sheet comes in contact with a widthwise center of the sheet of the small sheet.
Specifically, this image reading apparatus is provided with the feed roller movable in a direction orthogonal to the sheet feeding direction. That is, the feed roller is moved widthwise in skimming through the sheets mixedly stacked on a document tray, i.e., the stacking portion, so that the feed roller comes into contact with the widthwise center of the small sheet to suppress its skew. Meanwhile, the large sheet is skimmed through while suppressing its skew by restricting the sheet widthwise by a restricting plate.
Thus, the sheet is fed askew unless the feed roller is moved such that the feed roller comes in contact with the center of the sheet width of the small sheet in skimming through the different sizes of sheets stacked mixedly on the document tray in the image reading apparatus disclosed in Japanese Patent Application Laid-open No. 2000-118744. Then, in order to prevent the skew, an operator (user) has to move the feed roller by himself/herself every time in changing sizes of the sheets, and the apparatus has to be halted to move the feed roller every time when the feed roller is moved. Thus, it has been time-consuming and cumbersome to carry out such operation.